Twinning-induced energy-lowering structural transformation of Σ5 001 (210) grain boundary: A pathway to grain-boundary relaxation

HT Xue and ZJ Zhang and ZL Hu and JQ Ren and FL Tang and Y Zhang and XF Lu and JC Li, ACTA MATERIALIA, 288, 120829 (2025).

DOI: 10.1016/j.actamat.2025.120829

Nanograined (NG) metals generally lack structural stability owing to the instability of high-density grain boundaries (GBs) contained therein. Mechanically induced GB relaxation (M-GBR) was demonstrated to be effective in stabilizing the face-centered cubic (FCC) NG-metals. However, being a potential pathway to M-GBR, the underlying mechanism of the E5-to-E11 GB structure transformation remain unclear. In this study, uniaxial tensile deformations on the E5 001(210) symmetric tilt GB of FCC Ni and Cu were performed using molecular dynamics simulations. We found that both the Ni and Cu E5 GBs can change into the E11 110(113) GBs under tension. The E5-to-E11 GB structure transformations are energy-lowering processes, leading to GB stabilization. The underlying mechanism of such GB transformations was attributed to the deformation twinning induced change in the grain orientation. The difference between the GB transformations of Ni and Cu was that the Cu E5 GB required larger strain. During the deformation twinning, the distinct atomic sources between impinged GB1-1 and non-impinged GB1-2 and between GB1 and GB2 for constituting the structural units of transformed GBs were the underlying reason for the formation of single-layer GB disconnections on the transformed GB1 and for the migration of the transformed GB2. The lower average migration rate of the transformed GB than the initial GB indicated the reduced GB mobility after GB transformation. The twinning-induced energy-lowering GB structure transformation provides an alternative insight into the M-GBR mechanisms and models of FCC NGmetals.

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